Galvanic cells of the Leclanche or zinc chloride type typically employ an active cathode material which is primarily comprised of powdered electrolytic manganese dioxide ("EMD"). Because electrolytic manganese dioxide is a poorly conductive material a conductive material, such as graphite or carbon black, is generally incorporated into the cathode mix in order to impart sufficient conductivity to the cathode for most cell applications. Typically, active cathode material to conductive material weight ratios of about 4:1 to about 7:1 are employed in zinc chloride cells, with slightly higher ratios being employed in Leclanche cells. While increasing the active cathode material to conductive material ratio will improve a cell's light drain performance (as more active material is placed within the cathode mix), the resulting decrease in conductivity may greatly impair such cell's heavy drain performance.
Because devices which employ Leclanche or zinc chloride type galvanic cells are usually designed so as to accommodate cells of certain dimensions, there is generally a fixed volume within a cell's housing which is available for the cathode mix. Consequently, it is not possible to increase the light drain service of such cells by simply adding more cathode mix having a relatively low ratio of active cathode material to conductive material. Thus it would be desirable to provide higher ratios of active cathode material (i.e. EMD) to conductive material in the cathode mixes of Leclanche and zinc chloride cells so as to improve such cells' light drain service without impairing their heavy drain service.
It is therefore an object of this invention to provide a galvanic cell of the Leclanche or zinc chloride type having a cathode mix possessing an increased EMD to conductive material ratio (and therefore improved light drain service), which cell additionally exhibits good heavy drain service.